Under cold start conditions, a powertrain may be cooler than ambient conditions due to its larger thermal inertia. The engine upon startup has to overcome the lower powertrain temperature, and consequently, the time taken to reach an optimum operating temperature increases. This delay in reaching engine operating temperature may decrease fuel economy, increase engine wear, and increase exhaust emissions.
An example approach is shown by Murray et al. (U.S. Pat. No. 6,779,737) to enhance engine warm-up by preheating the engine when not in use. Engine oil and engine coolant are guided through a fluid heater, warmed, and later circulated across the engine and through the transmission. The fluid heater uses gasoline fuel to heat the engine oil and coolant. The vehicle compartment can also be heated by flowing the warmed coolant through a heater core.
However the inventors herein have identified potential issues with the above approach. For example, the fluid heater in U.S. Pat. No. 6,779,737 uses fuel to heat the engine oil and coolant resulting in increased fuel consumption and costs. Further, the fluid heater is an extra component that reduces available space.
The inventors herein have recognized the above issues and identified an approach to at least partly address the issues. In one example approach, a method for heating a powertrain in a parked and shut down vehicle, prior to an engine start, is shown. The method comprises, prior to an engine start and when a temperature of the powertrain is lower than ambient temperature, heating a coolant by circulating it through a radiator and operating an electric radiator fan, and then flowing the warm coolant across the powertrain. In this way, heat from the ambient air may be absorbed by the coolant and transferred to the powertrain.
For example, when a vehicle is parked outdoors and shut down with an engine at rest, a controller may be activated by a timer at regular intervals to monitor ambient temperature and a temperature of a powertrain. If the ambient temperature is higher than the powertrain temperature, and the difference in said temperatures is more than a threshold, the controller may initiate a procedure to warm the powertrain, prior to an engine start. An electric coolant pump and an electric thermostat may be activated to allow coolant circulation. The coolant may be circulated through a radiator while an electric radiator fan is operated to draw ambient air across the radiator exterior, thus enabling the coolant to absorb heat from ambient air. The warm coolant may be further circulated across the powertrain to preheat the powertrain.
In this way, a powertrain within a parked vehicle may be prevented from cooling below ambient temperature. By monitoring the powertrain temperature along with ambient conditions at regular intervals following vehicle shut down, the powertrain may be maintained at a temperature close to ambient, thus reducing the energy used for engine warm-up upon engine start. Since the coolant is warmed by absorbing heat from ambient air, fuel consumption remains largely unaffected. Further, by using existing components for preheating the powertrain, additional expenses can be avoided and space savings can be achieved.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.